fix(ci): render infra config

[universal-itengineer]

Description

Fixes the infrastructure configuration rendering for nested e2e clusters by correcting the YAML structure and the Helm template lookup logic.

Changes:

• Fixed YAML indentation in e2e-reusable-pipeline.yml - moved networkConfig to the correct nesting level
• Fixed _helpers.tpl to properly extract networkConfig from the instances values using get function instead of incorrect dig call

Why do we need it, and what problem does it solve?

The previous implementation (#2181) introduced SDN configuration for nested e2e clusters, but the YAML structure was incorrectly nested and the Helm template was unable to properly access the networkConfig values. This caused the clusterNetworkName to be empty, preventing VMs from connecting to the configured ClusterNetwork.

What is the expected result?

1. The networkConfig block is correctly rendered in the infra values YAML
2. The Helm template properly retrieves networkConfig.clusterNetworkName from instances
3. VMs in nested e2e clusters can use the configured ClusterNetwork for additional network interfaces

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: ci
type: fix
summary: Fix infrastructure config rendering for nested e2e clusters
impact_level: low